docs: describe about the flint data provider types

[Namyalg]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

• [X] Issue reference: #168
• [X] Peer reviewer: @chicken-biryani @HarshCasper
• [X] Preview Links: https://docs.moja.global/en/latest/Understanding-FLINT/data-preparation/index.html#data-provider-types
• [X] Explain the changes: Added an elaborate description of the flint provider data types raster and vector

Thanks for opening the Pull Request for moja global. Happy contributing ✨

[shloka-gupta]

Great additions @Namyalg. A thought, do you think information about how we use it in FLINT should come in a different paragraph?

[Namyalg]

Yes @chicken-biryani , I will separate the introduction to the datatype, and how it is used in FLINT